Hong Kong -LRB- CNN -RRB- -- The screech of clear , heavy-duty duct tape scratches on the ear even before the mass of mainland Chinese visitors comes into view .

This is the daily soundtrack from thousands of people packing up brown cardboard boxes outside Sheung Shui train station , the last rail stop in Hong Kong before mainland China .

Every day these mainlanders make a Hong Kong entrance , picking up goods on behalf of China-based agents .

Every evening , they make an exodus back across the border , taking with them sundry items that include Hong Kong-made baby formula and Huggies diapers to beauty masks and bottled Starbucks frappucinos .

Some call these people `` grey traders . '' Others call them `` mainland mules . ''

Local residents call them a nuisance .

Steven So , chairman of Hong Kong 's North District Council for the past five years , says the daily horde makes his constituents angry .

`` They 're mad because these visitors make a big mess . They litter . They throw their used lunchboxes everywhere . They spit . They block the walkways . They even injure people when they bump into them with their trolleys , '' he says .

So says it has as much to do with trust as it does with tariffs over the past few years .

Food scandals in mainland China , including the 2008 tainted baby formula scare in which more than 53,000 infants were reported ill , have pushed many consumers to buy products made elsewhere . Hong Kong goods are considered to adhere to stricter quality guidelines .

Many products in Hong Kong have also become cheaper than the same ones found in mainland China . Since 2005 , China 's currency , the yuan , has strengthened 25 % against the U.S. dollar , to which the Hong Kong dollar is pegged .

And if goods are ferried over in a piecemeal fashion by mainland day traders -- box-by-box versus traditional cargo containers -- importers can avoid commercial tariffs that average 50 % . Taxes on electronic goods can reach as high as 70 % , adds So .

That kind of savings keeps the cross-border grey trade very much alive .

`` These mainland Chinese visitors buy anything and everything -- as long as it 's not ` made in China , ' '' says So .

About a 20-minute walk from the train station , at a non-descript but well-known warehouse for this industry , hundreds of mainlanders swarm the building as they pick up their goods bound for China .

Sweaty workers wheel out pallets of boxes that advertise instant noodles and diapers made in Japan . Grey traders -- men , women , young and old -- then put them on small handcarts and walk to the train station .

While no one would give their full name , one worker revealed he earns HK$ 100 , or about U.S. $ 12 , per round trip . He admitted it is not much money but it is enough to take care of his family . His wife , a Hong Kong citizen , just gave birth to their first baby .

One lady who only identified herself by her surname of Lau said that they all face pressure at customs as well . `` If our goods get turned away at the mainland border , we just have to dump them . So there 's risk in this business , '' she says .

There is also risk -- and reward -- for regular border area businesses .

Pharmacies , convenience stores and jewelry shops have welcomed the rise in demand .

Shop worker salaries have doubled in the past two years to cater to the surge of shoppers . But rents for retail space have tripled in the past three years and inflation is a chronic concern , according to various neighborhood shop owners .

Aside from the economic woes , residents cite other issues that include hygiene , environmental and crowd complaints .

In recognition of rising anti-China animosity from Hong Kong , Beijing shelved a controversial plan earlier this month that would have opened the door to millions more mainland visitors to the city .

Four million people from Shenzhen alone - right across the border - would have been eligible under the proposed program .

Many Hong Kong citizens are upfront with their emotions about their mainland cousins .

`` Angry . Annoyed , '' said local resident Gabi Liu . '' -LRB- There are -RRB- too many people around us disturbing our country . Most of them are being bad-mannered . ''

Steven So , the district chairman , is more nuanced .

Hong Kong is an `` open '' city that does welcome conventional tourists who stay at hotels , eat at restaurants and visit the city 's theme parks like Disneyland , he says .

But he also holds a caveat for non-conventional tourists -- those grey traders who hold multi-entry visa holders that crisscross the border each day .

`` We need to weigh the pros and cons . To us in this district , the cons outweigh the pros . We do n't have room for more people . ''

Still , he may be talking against a tide that can not be turned .

In 2011 , Hong Kong , a city of 7 million people , saw 28 million mainland visitors -- two thirds of the city 's total visitors , according to the Hong Kong Tourism Board .

That is expected to grow even more , further reinforcing the reality that Hong Kong 's economy is wedded more to mainland China as the years pass for this former British colony .

Vivian Kam contributed to this report .

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Every day thousands of mainland Chinese go to Hong Kong to buy goods

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They 're paid by agents to meet demand for non-Chinese , cheaper products

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Residents near the border complain that they 're a nuisance